With the recent development of a binocular, three-dimensional vision facility at SRI that can independently stimulate and accurately measure the responses of the extraocular (horizontal and vertical version and vergence) and intraocular (pupil and accommodation) muscles simultaneously in both eyes, the dynamic characteristics of each of these ocular subsystems and the interactions among them can be studied in depth for the first time. The accommodation system, with its poorly defined stimulus and detection mechanism, is of special interest as is the influence of tremor, drift, flicks, pupil, and accommodative fluctuations and certain unequal oculomotor responses (in the two eyes) in the maintenance of binocular vision. The characteristics and interactions of the extraocular and intraocular muscle systems will be studied both by selectively stimulating a single system, while either altering or eliminating the influence of other systems with stabilization techniques, and by using stimuli that produce a conflicting or abnormal demand on the system under study.